Combined process for hydrotreating and catalytic cracking of residue

Abstract

Disclosed is a combined process for hydrotreating and catalytic cracking of residue, wherein the residue, catalytic cracking heavy cycle oil with acidic solid impurity being removed, optional distillate oil and adistillate of catalytic cracking slurry oil from which the acidic solid impurity is removed are fed into residue hydrotreating unit, the hydrogenated residue obtained and optional vacuum gas oil are fed into catalytic cracking unit to obtain various products; the catalytic cracking heavy cycle oil from which the acidic solid impurity is removed is circulated to the residue hydrotreating unit; the catalytic cracking slurry oil is separated by distilling, the distillate of the catalytic cracking slurry oil after removing off the acidic solid impurity is circulated to the residue hydrotreating unit. This process makes the residue hydrotreating and catalytic cracking being combined together more effectively such that it is not only able to improve product quality of the residue hydrotreating, elongate operation cycle of the residue hydrotreating unit, but also increases the yield of the hydrogenated diesel oil and catalytic cracking light oil, and decreases coking quantity of the catalytic cracking.

Description

TECHNICAL FIELD[0001]The present invention relates to a process for treating hydrocarbon oil by using one hydrotreating process and another one conversion step, more particularly, a process for combining both hydrotreating process and catalytic cracking process of residue.TECHNICAL BACKGROUND[0002]Currently, the world is facing a trend that crude oils turn to heavy and poor in quality increasingly, and requirement for heavy fuel oils is decreased down gradually, while requirement for light oils is increasing greatly. Therefore, refinery enterprises are pursuing the maximization of converting residue.[0003]In various processes of lightening residue, it is a good process that residue is hydrotreated in advance, and then the hydrogenated tail oil obtained is further processed by catalytic cracking. After being hydrotreated to remove impurities such as metal, sulfur, nitrogen and the like, the residue has an increased hydrogen content and can be used as a superior-quality feedstock for ...

AI Technical Summary

Benefits of technology

[0042]Said catalytic cracking recycle oil or catalytic cracking heavy cycle oil is processed by using a combination of one or more methods selected from the group consisting of fine filtration, centrifugation, distillation or flash separation to remove the acidic solid impurity. The catalytic cracking recycle oil or catalytic cracking heavy cycle oil is preferably processed by using fine filtration to remove the acidic solid impurity, because the fine filtration method has higher efficiency and lower cost for running.

[0048]Residue hydrotreating is a diffusion-dependent reaction, and thus the viscosity is an essential factor that influences hydrotreating reaction of the residue, especially, the vacuum residuum with high viscosity. Addition of the catalytic cracking recycle oil, especially catalytic cracking heavy cycle oil, results in decreasing viscosity of the feedstock for residue hydrotreating, increasing diffusion rate of residue molecules into micropores of the catalyst, and thereby accelerating hydrodemetallization reaction of impurities such as metal and the like. In addition, in contrary with hydrogenation unit of distillate oil, the residue hydrotreating unit has serious carbon deposit at the tail end of the catalyst bed, furthermore, the more close to outlet of the reactor, the more carbon deposit is formed. This is primarily in that colloid and oil constituents have a fast hydrogenating-saturation speed, while asphaltine has a slow hydrogenating-saturation speed and is easy to breaks off side chains with only aromatic nuclei with the highest aromaticity remaining. Therefore, the solubility becomes less and less in the environmental solvent of which saturation degree becomes higher and higher, and finally carbon deposit is easy to be formed on the catalyst by settling. If catalytic cracking recycle oil having high aromaticity is added, especially a catalytic cracking heavy cycle oil, the aromaticity of ambient solvent may be increased, peptizing power of asphaltine may be increased, and deposition on the catalyst at tail end of the bed can be decreased. In addition, partially hydrogenated products of polycyclic aromatics in the catalytic cracking recycle oil, especially in the heavy cycle oil are very strong hydrogen-donators that are able to decrease condensation of thermal free radical of the residue and suppress the formation of coking precursor. These all can greatly decrease carbon deposit on catalyst, reduce deactivation rate and elongate operation cycle.

[0049]Therefore, the catalytic cracking recycle oil, especially the catalytic cracking heavy cycle oil, from which solid acidic particulate substance has been removed, is circulated to the residue hydrotreating unit and treated before being used as a catalytic cracking feedstock. As a result, the detrimental effect brought along with the solid acidic particulate substance is eliminated, inherent properties of ability peptizing asphaltine and the like are maintained, and improvement of running all the residue hydrotreating unit and catalytic cracking unit is brought about.

[0054]1. The process according to the present invention can make the catalytic cracking recycle oil, especially the catalytic cracking heavy cycle oil before entering the residue hydrotreating unit to remove out the catalytic cracking catalyst powder, avoiding disadvantageous factors brought about with the catalytic cracking catalyst to the residue hydrotreating unit, including decreasing down the reaction effectiveness of residue hydrotreating and shortening operation cycle of the residue hydrotreating, and make a more effective combination of hydrotreating and catalytic cracking of residue able to be realized.

[0055]2. Adding catalytic cracking recycle oil, especially catalytic cracking heavy cycle oil, from which catalyst particulate substance is removed, to the residue, in particularly vacuum residuum, may result in decreasing feedstock viscosity in a large amplitude, increasing reactant diffusivity and reaction rate of removing impurity, and decreasing the content of sulfur, nickel and vanadium in formation oil, or increased greatly the feedstock space velocity provided that properties of the hydrogenating formation oil are ensured from variation. Meanwhile, carbon deposit may be further suppressed on the hydrogenation catalyst, activity of the residue hydrotreating catalyst is increased, and operation cycle of the residue hydrotreating unit is elongated.

[0056]3. After the catalytic cracking recycle oil, especially catalytic cracking heavy cycle oil, is hydrogenated, its sulfur content may be decreased, so the sulfur content of its catalytic cracking gasoline and diesel oil may be decreased; after the catalytic cracking heavy cycle oil is hydrogenated, its saturation degree and hydrogen content may be increased, so yield of light oil (here represents the sum of liquefied gas, gasoline and diesel oil) is increased, displaying as increased in yield of hydrogenated diesel oil and catalytic cracking light oil; meantime, coking quantity of catalytic cracking is decreased, treatment capacity of the catalytic cracking unit is increased.

Problems solved by technology

Currently, the world is facing a trend that crude oils turn to heavy and poor in quality increasingly, and requirement for heavy fuel oils is decreased down gradually, while requirement for light oils is increasing greatly.

However, as heavy cycle oils, decanted oils and the like contain polycyclic aromatics, the yield of light oil is lower, the coking quantity is higher, so that the load of the regenerator is increased, and the treatment capacity and economic benefit of the catalytic cracking unit of heavy oil are decreased.

In addition, the heavy cycle oil has a sulfur content about one more time higher than the hydrogenated tail oil, the circulation of the heavy cycle oil also results in increasing sulfur content of products and sulfur emissions.

There are still problems for the hydrogenation unit, such as, poor operational stability and like.

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